The Whitehead Institute requests $500,000 for the purchase of a Zeiss LSM710 scanning confocal microscope, to be located in the W.M. Keck Core Facility, and made available to both Whitehead and MIT investigators. Scanning confocal microscopes allow optical sectioning of living and fixed material, so that investigators can image deep into a solid sample, and make a 3D reconstruction of the sample. The instrument requested is of great importance, as it will replace an out-dated, nine year old Zeiss LSM510, currently the only scanning confocal microscope at the Whitehead Institute. Deterioration of the current LSM510 has begun to hamper research, as repair times on this instrument have become excessive, replacement parts cannot be obtained, and the system cannot support upgrades. Our choice of the Zeiss LSM710 as a replacement for the LSM510 is due to the large number of outstanding features on the LSM710, its ease of use, and Zeiss'excellent customer support. Some of the new features offered by the LSM710 include a 405nm wavelength laser, which, in conjunction with the LSM710's five other lasers, allows simultaneous multi-imaging of up to ten different dyes;a new spectral recycling loop and a twin gate beam splitter which will increase sensitivity significantly, enhancing our ability to perform live imaging without phototoxicity. A tunable pulsed laser with a capacity from 488-640nm will be purchased for the LSM710 through a financial commitment of $212,587 from the Whitehead Institute. This tunable laser allows Fluorescence Lifetime Imaging (FLIM), which enables study of molecular lifetime, and facilitates FRET (Fluorescence Resonance Energy Transfer) analyses, to determine molecular interactions. The LSM710 can perform FRAP (Fluorescence Recovery After Photobleaching) to analyze molecular dynamics;calcium imaging is simple and targeted uncaging of fluorescent indicators or bioactive molecules is readily feasible. New Zen software that comes with the LSM710 will simplify previously arduous tasks, such as deconvolution, ratio imaging, and photobleaching analysis. In addition to purchasing FLIM equipment, the Whitehead Institute will contribute to the yearly service contract for the LSM710, and to salary support for two technicians who train users and oversee use of the instrument. By expanding the experimental approaches available to researchers, the LSM710 will contribute greatly to the success of many NIH-funded projects, including the analysis of neural degeneration, nervous system development and birth defects, mental health disorders, immune function, meiosis and associated chromosomal abnormalities, cancer, metabolic regulation, regeneration and identification of stem cells. Acquisition of the LSM710 will allow researchers to address these important biomedical issues, and the outcomes of this research will include new diagnostics and therapeutics, in accord with the mission of the NIH.